Amplification circuits are used in various applications such as switched capacitor filters, analog-to-digital converters, and general communications circuits. The particular amplification circuit chosen depends on numerous considerations such as noise level in the amplifier output, bandwidth of the amplified signal, and the magnitude of the voltage supply connected to the amplifier. Conventional amplifier circuits, however, each provide limitations concerning the above-listed considerations. For example, certain amplifiers are only operable for low clock rates and, hence, are not useable in systems where higher clock frequencies (e.g. 10 MHz) are implemented. In particular, these amplifiers include internal component configurations which give rise to substantial phase shifts and, thus, prohibits the device from being used in high frequency applications. Another common problem with known amplifier circuits is that the supply voltage must be adjusted relatively high in order to prevent the amplification components of the circuit from turning off under various circumstances. Still another problem is the difficulty of maintaining a sufficient biasing current in the amplification circuit without providing excess current and wasting power in the circuit.
Each of the limitations of these prior art amplification circuits provides a corresponding limitation in any application in which the circuit is used. Therefore, a need exists for an amplification circuit which is operable to operate at a substantially low power supply voltage, utilize an efficient amount of current, provide high frequency operation, and significantly reduce the amount of input reference voltage noise that is generated by the circuit.